The present invention relates to the application of face gears to helicopter transmissions.
More specifically, the present invention relates to a transmission interposed between the engines and the main rotor of a helicopter, for achieving a given velocity ratio between the output shafts of the engines and the drive shaft of the main rotor, and for controlling rotation of both the tail rotor and the input shafts of the helicopter accessories.
For achieving said velocity ratio, known transmissions of the above type feature a number of ordinary, normally bevel gears meshing with one another to define, in most cases, two input speed reduction stages, and which are normally associated with an epicyclic gear train defining a third reduction stage.
Though reliable and still widely used, known transmissions of the above type present a major drawback in terms of weight and size, mainly due to the large number of component parts involved, which, among other things, also entail relatively time-consuming, high-cost assembly and setup operations. Also, by virtue of comprising a large number of moving parts, known transmissions are invariably a major source of noise.